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Old 07-23-2021, 11:37 AM   #1
Mini-Skoolie
 
Join Date: Jun 2021
Location: Dallas, Tx
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Year: 2001
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Battery Upgrade Time

Batteries are batteries right?
Ok no its not that generic of a question :P.

Im looking to upgrade from the golf cart batteries that came with it, 6 - 6v 235ah wired to make a 12v setup, to lithium. In theory, I could get 4 - 12v 300ah batteries and it would just boost my reserves and longevity of use right?

Or, is there a benefit over more over all smaller ah batteries?

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Old 07-23-2021, 11:45 AM   #2
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What are you upgrading your batteries for, what are you hoping to get out of it?
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Old 07-23-2021, 11:53 AM   #3
Mini-Skoolie
 
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I don't know how well they were maintained beforehand, but they seem to have less capacity than it should based on the little bit that I use them off shore power. To the point where I know they should be charged 100% and I switch from plugin to battery the monitor instantly says its at 50% or less.
Ill double check the date, but they have been used for a couple years at least with consistent use.

This is also in preparation to build out for solar later on, as well as run AC off them in short bursts.
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Old 07-23-2021, 12:04 PM   #4
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What kind of monitor are you using? If its voltage based, they are very much unreliable. Might consider adding a shunt-based meter if that's the case.


Could you clarify on your original questions? The bank proposed (4x 300Ah 12V in 12V config) has roughly 1.7 times the capacity of the bank described (6x 235Ah 6V in 12V config). Likely more if the 6V batteries are well aged or have been abused.


I would coincide the battery upgrade with a solar buildout if you can- that way the batteries are tailored for that use case.
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Old 07-23-2021, 12:23 PM   #5
Mini-Skoolie
 
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Ill have to check and see which one it was, some kinda monitor that is 3rd party, its separate from my control panel for the inverter/charger.

Ideally it would be enough to run 2 AC units in the summer (and a decent heater in winter), on demand water heater, fridge, and tv while driving.

Depending on the cost, I planned on putting enough panels to handle all that. Its a 40ft bus with nothing by 1 AC and 1 hatch so I have the space.

Longevity, I mean in general lithium will last longer than replacing with like-for-like lead acid.
Reserves, longer drives we can run the rooftop ac in spurts. I do have a small, 3500watt, generator I plan to use when able to to power such things as well.
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Old 07-23-2021, 12:37 PM   #6
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Quote:
Originally Posted by Mtrx804 View Post
Ideally it would be enough to run 2 AC units in the summer (and a decent heater in winter), on demand water heater, fridge, and tv while driving.
Lets break this out...
  • 2 AC units - During full sun this is easy. During off-hours this is quite hard. The battery bank proposed (14kWh lithium) will give you one, maybe two night of standby running AC without generation.
  • "decent heater in winter" - the only pure electric heaters that are realistic to run off of batteries are heat pumps... you will want gobs of battery and will need to keep your panels clear of snow. Diesel heaters are a much more economic option if they fit your uses, and lots cheaper.

    Any climate control based purely on battery power for use while driving is generally unrealistic. Maybe if you isolate the driver.
  • on demand water heater - I recommend propane. Electric is pretty insane, with _low end _ heaters starting in the 3kW range.
  • Fridge/TV- is pretty easy by comparison



Quote:
Originally Posted by Mtrx804 View Post
Depending on the cost, I planned on putting enough panels to handle all that. Its a 40ft bus with nothing by 1 AC and 1 hatch so I have the space.
Panels are cheap, fill your roof.



Its the batteries that will bring the big costs. I have a little over 3x the size battery of the one you proposed (4x, 12V, 300Ah Lithium), I am hoping to do heat pump off solar this winter. Last winter I was not able to, this time we'll see.
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Old 07-23-2021, 12:40 PM   #7
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Quote:
Originally Posted by Mtrx804 View Post
Batteries are batteries right?
Ok no its not that generic of a question :P.

Im looking to upgrade from the golf cart batteries that came with it, 6 - 6v 235ah wired to make a 12v setup, to lithium. In theory, I could get 4 - 12v 300ah batteries and it would just boost my reserves and longevity of use right?

Or, is there a benefit over more over all smaller ah batteries?
Good question. I'm also curious how some of the larger systems were configured. I'm being lazy right now, but I'm guessing a search on the build threads might show how some of the bigger systems are designed.
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Old 07-23-2021, 12:56 PM   #8
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Being in Tx anything we can do to alleviate some of the heat in the middle of the day on the move is better than nothing. We tried to run a fan and it helped but it just wasn't enough. We intend to isolate the front 1/4 of the bus where the roof unit is and drive that way.
We've also setup the back 1/4 so we can shut it off to the rest when we sleep and use a portable AC or heater.
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Old 07-23-2021, 01:04 PM   #9
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Good question. I'm also curious how some of the larger systems were configured. I'm being lazy right now, but I'm guessing a search on the build threads might show how some of the bigger systems are designed.
I've found some information here and there, but nothing specific for my current setup I'm trying to build. By build I mean upgrade what was here economically.

I think I'm limited by the 30amp system that was originally installed. The wiring doesn't appear to be thick enough to handle just upgrading the components to make it a 24v or higher system. I'm trying to get creative, to the point where i considered a generator with multiple 30amp plugins and separating out higher usage appliances.

I am all ears to anyone who would like to talk me through any of this. I'm 100% new to all this, I only know what Google told me lol.
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Old 07-23-2021, 01:09 PM   #10
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Originally Posted by Mtrx804 View Post
The wiring doesn't appear to be thick enough to handle just upgrading the components to make it a 24v or higher system.
A 24V system requires _less_ thick wiring than an equivalent 12V system, and a 48V system _less_ thick wiring than an equivalent 24V system, not the other way around.

I have a comparatively large system meant for full time off grid use, I went with 48V for the benefits of lower amp draw, cheaper components, higher efficiency.

Quote:
Originally Posted by Mtrx804 View Post
I'm trying to get creative, to the point where i considered a generator with multiple 30amp plugins and separating out higher usage appliances.
AC and DC are different aspects of a system, and I would encourage looking at them in isolation somewhat to better understand the problems at play.

Quote:
Originally Posted by Mtrx804 View Post
I am all ears to anyone who would like to talk me through any of this. I'm 100% new to all this, I only know what Google told me lol.
If you want we can have a phone conversation or something to sort out some of your questions...
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Old 07-23-2021, 02:58 PM   #11
Mini-Skoolie
 
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Originally Posted by kazetsukai View Post
If you want we can have a phone conversation or something to sort out some of your questions...
Winnie the Hoobus is in storage right now, but I plan to pick it up tonight. I would greatly appreciate any time you can spare.
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Old 07-23-2021, 03:55 PM   #12
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Winnie the Hoobus is in storage right now, but I plan to pick it up tonight. I would greatly appreciate any time you can spare.
Go ahead and PM me when you want to set something up.
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Old 07-23-2021, 06:04 PM   #13
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Originally Posted by kazetsukai View Post
Go ahead and PM me when you want to set something up.

I recommend that you listen to Kaz and ask any questions that come to mind. And rite down any advice given...
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Old 07-28-2021, 04:58 PM   #14
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Quote:
Originally Posted by Mtrx804 View Post
Batteries are batteries right?
Ok no its not that generic of a question :P.

Im looking to upgrade from the golf cart batteries that came with it, 6 - 6v 235ah wired to make a 12v setup, to lithium. In theory, I could get 4 - 12v 300ah batteries and it would just boost my reserves and longevity of use right?

Or, is there a benefit over more over all smaller ah batteries?
Going from lead acid to lithium alone will give you an increased capacity. Lithium batteries have a considerably higher depth of discharge limit.
That being said you have other losses to consider. A 12v system is the least efficient in conversion to 120 ac. Consider going to 24v using the higher ah batteries the amount of useable life will be extended.
This being said a bit of calculation is what you need to determine what you need to get satisfaction. Ruth and I live in a completely solar powered bus conversion. We live were it is hot all day and well into the night. Our mini split runs constantly. Along with other continuous loads like refrigerator and freezer. I have an oxygen concentrator that runs all night. When I look at my load meter it is between 1.3k and 2.1k. Averaging 1.8k at night. If you are on solar you have a point in the day where there solar is no longer keeping up and you are drawing on your batteries. You count from then to the point in the day when your solar is charging your batteries and running your loads. This is the minimum number of hours you need. Multiply that number of hours times your max load. In our case 2.1k x 13 hours a day. We need 27kwh of storage to run day and night with assurance of no interruptions. Our average use is about 18kwh per night but as much as 27kwh. That also means you've got to be able to produce that during the daylight hours for your system to recover for the following night.
We built our system playing the catchup game. Not enough? Add more. We only did it that way because we couldn't afford to build what we had already calculated was what we needed. At this point our system is just a little bigger than what we calculated but we didnt allow for overcast weeks when we did the calculations. Overcast weather drove the size of our solar array to be 40% larger than what is needed 90%of the time to allow for our monsoon season.
By the way you calculate your own by multiplying your volts x your apps. A 300ah lithium iron battery will provide about 200 useable amp hours. With a 24 volt system you get 200 x 24 you get 4.8k now multiply that to get your required storage for us that is 6 batteries in a 6p configuration.
We would love to have 4 more batteries and 2k more panels.
Right now we get by comfortably but we have occasional very hot cloudy weeks wher we have to turn off the air conditioning by 2 am and wait for 8 am to turn it back on or risk low battery alarm from our inverter.
One note. Our powerjack inverter while being efficient, well suited for starting heavy loads like motors and welders, and really inexpensive, less than 500 bucks, was designed for lead acid batteries. It will not draw as much from our lithium batteries as it could. The low battery cut off is designed to protect your lead acid batteries from a depth of discharge greater than 70% lithium batters can be drawn much lower without damage.
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Old 07-28-2021, 05:10 PM   #15
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Quote:
Originally Posted by Rock-N-Ruth View Post
Overcast weather drove the size of our solar array to be 40% larger than what is needed 90%of the time to allow for our monsoon season. It
This is why I tell folks to get as many panels as they can afford/fit...



Last week there was 5 consecutive days of overcast which finally depleted us to around 20%, so I had to charge from grid. Most of the time we are playing "catch up" as you say- barely winning the generation/consumption game. Conclusion: Need more panels.


Hope to see you guys on the road one day!
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Old 07-28-2021, 05:14 PM   #16
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Quote:
Originally Posted by Mtrx804 View Post
I've found some information here and there, but nothing specific for my current setup I'm trying to build. By build I mean upgrade what was here economically.

I think I'm limited by the 30amp system that was originally installed. The wiring doesn't appear to be thick enough to handle just upgrading the components to make it a 24v or higher system. I'm trying to get creative, to the point where i considered a generator with multiple 30amp plugins and separating out higher usage appliances.

I am all ears to anyone who would like to talk me through any of this. I'm 100% new to all this, I only know what Google told me lol.
I hope you saw the good news in the other comment on this forum: the that 24 and 48 VDC systems can safely use the existing wiring because the same power over the wire can be carried with lower current, due to the higher voltage. So no rewiring needed, just different fusing needed if you go the higher voltage route.

This is provided that your existing wiring is all sized correctly. If you did not install it your bus wiring I recommend doing a wiring diagram with wire size and length, and current requirements for all devices, and making sure your conductors are all properly sized.

You mention you are limited by the '30 Amp system currently installed'. Note that battery capacity can be increased almost without limit without changing your existing system. You could put a thousand amps of battery storage in, and as long as your fusing between the battery and the main distribution point is properly sized, your existing electrical doesn't need to change.

Greater battery capacity means your ability to stay off grid is increased, proportional to the increase in batteries.

If you want to use more power (higher current devices), or add more branch circuits, then yes you probably need to touch the existing 30 amp system. But if your needs are met with the existing system and all you need is for it to last longer into the night you can simply add batteries and recharge capability.
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Old 07-28-2021, 11:57 PM   #17
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Quote:
Originally Posted by Mtrx804 View Post
Batteries are batteries right?
Ok no its not that generic of a question :P.

Im looking to upgrade from the golf cart batteries that came with it, 6 - 6v 235ah wired to make a 12v setup, to lithium. In theory, I could get 4 - 12v 300ah batteries and it would just boost my reserves and longevity of use right?

Or, is there a benefit over more over all smaller ah batteries?



" golf cart batteries that came with it,"


Is this your starter battery or a house battery
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Old 08-01-2021, 01:32 PM   #18
Mini-Skoolie
 
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Originally Posted by kazetsukai View Post
Go ahead and PM me when you want to set something up.
I haven't forgotten to reach out, had to take the bus to a mechanic for a leak coming from the front seal. Sorry for such a delay.

You wouldn't believe how hard it is to find a good, well reviews, and communicative diesel mechanic in the DFW area who has a shop large enough to pull a bus in.
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Old 08-01-2021, 01:35 PM   #19
Mini-Skoolie
 
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Quote:
Originally Posted by kidharris View Post
" golf cart batteries that came with it,"


Is this your starter battery or a house battery
House, the batteries that run everything inside. The starter ones are a couple bigger off the shelf AutoZone ones. I haven't looked at them much, they were labeled with recent dates so I didn't commit it to memory yet.
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