12v to 12v battery tender?

[ermracing]

I keep my motorcycle in the back of my bus and want to install a battery tender for it. The problem is that all the tenders I've found plug into 120v AC. I have a 12v battery bank (solar) so I'd like to go direct to those so I don't have to have my inverter running all the time, just to power the battery tender.

I could simply install a set of jumper between my 12v battery bank and the motorcycle battery, but that means it will now be part of the bank and be effected by the bulk and overcharging the solar controller does. I don't think that would be good for the motorcycle battery.

How can I create a 12v tender that connects to the 12v bank, or do I just get a small low amp inverter and plug a 120v tender into that?

[rossvtaylor]

I would get a small DC>DC charger, as it will monitor the battery state and vary the charge accordingly. I like the Victron Orions, but I think the smallest they make is a 30A version and it's about $225. The Sterlings are fantastic but I think their cheapest one is about $400. These are all much larger in capacity than you need, though, so you might find a much cheaper option.

[Rwnielsen]

There is an inexpensive option that requires a little work, a solar battery tender.
I bought a cheap one that didn't work out (at all) so I bought a better one.


HERE

I also bought an inexpensive 30a charge controller to go with it (Renogy)

I just replaced both of my start batteries due to neglect on my part and trusting a crappy setup

[Rucker]

Search 'Tekonsha 2024-07-S Heavy Duty Quick/Maintenance Multi Stage Charger'

It's cheap, and is powered by 12VDC.

[ermracing]

Thanks Rucker, that looks like exactly what I want.

Also, thanks to Rwnielsen, that solar setup will work great for my truck batteries since I've kept them separate from the solar bank.

[Rwnielsen]

Originally Posted by ermracing

Thanks Rucker, that looks like exactly what I want.

Also, thanks to Rwnielsen, that solar setup will work great for my truck batteries since I've kept them separate from the solar bank.

The one I have now outputs around 2 amps peak for a couple hours on a sunny day. The Renogy charge controller is to modulate that. These solar charging kits generally come with a very cheap charge controller.

[rossvtaylor]

Originally Posted by Rucker

Search 'Tekonsha 2024-07-S Heavy Duty Quick/Maintenance Multi Stage Charger'

It's cheap, and is powered by 12VDC.

Has your experience with it been good? It's definitely a more affordable version of the ones I've used, but the capacity of those is way overkill for the OP's need. But I checked the Amazon reviews and there were several which concerned me a bit. I trust you more than those reviews, though.

[Rucker]

I've not used it-I probably should have noted I just did an Amazon search because it seems like it should be a dirt simple device and one shouldn't have to buy an expensive DCDC charger for the task.

For the price I'd probably buy two, in case one breaks out of the box.

[incubus]

They make solar cells just for battery tending. I have a 24 volt for starter batterys (off military vehicle) and bought a 3"x11" solar cell that maintains my 12 system. Works well and easy install.

[Rucker]

Originally Posted by incubus

They make solar cells just for battery tending. I have a 24 volt for starter batterys (off military vehicle) and bought a 3"x11" solar cell that maintains my 12 system. Works well and easy install.

Good alternative, and pretty simple solution though the quality of some of those devices is pretty questionable.

Military grade sounds a lot better...

[incubus]

A 12 volt unit is cheap, check the amperage output. The price climbs with amps. Really doesnt take much to maintain a battery. You're not charging it up just maintaining, so only requires a few amps

[Rwnielsen]

Originally Posted by Rucker

Good alternative, and pretty simple solution though the quality of some of those devices is pretty questionable.

Military grade sounds a lot better...

You should really upgrade the charge controller. A cheap Renogy 20a unit is light years ahead of the ones they come with.

[Iceni John]

I keep my two Group 31 start batteries constantly charged from the solar-charged house batteries by a pair of LSL Products Ultra Trik-L-Start battery maintainers: each start battery has its own Trik-L-Start, and each Trik-L-Start has a 10A self-resetting circuit breaker powered off the house batteries. I originally wanted to have a small charge controller for each start battery running off my solar array, but the CCs that I bought were overloaded by the solar panels, hence my second version of charging the start batteries from the house batteries. I like always seeing a green light for each start battery that tells me it's 100% charged; they're eight years old and still perfectly good, so the Trik-L-Starts are well worth it.

John

[Rucker]

Originally Posted by Iceni John

I keep my two Group 31 start batteries constantly charged from the solar-charged house batteries by a pair of LSL Products Ultra Trik-L-Start battery maintainers: each start battery has its own Trik-L-Start, and each Trik-L-Start has a 10A self-resetting circuit breaker powered off the house batteries. I originally wanted to have a small charge controller for each start battery running off my solar array, but the CCs that I bought were overloaded by the solar panels, hence my second version of charging the start batteries from the house batteries. I like always seeing a green light for each start battery that tells me it's 100% charged; they're eight years old and still perfectly good, so the Trik-L-Starts are well worth it.
John

They look great, but they are no longer available. The website is great for RV electronics, though it is terrible to navigate.
Here's the closest thing they now have, about $127:
https://www.bestconverter.com/Batter...l#.ZC7ZK3bMKUk

For a hundred bucks less I decided to buy a Tekonsha 2024-07-S Heavy Duty Quick/Maintenance Multi Stage Charger. They were on sale for $27. I actually bought two.

The same basic model is also listed as a 'newer item' for double the price, so I'm guessing the one I got is the cheapest DCDC solution for parasitic draw if you have a house battery on solar, at least for what's on the Internets at the moment, other than the unit with it's own little solar panel.

[Iceni John]

Originally Posted by Rucker

They look great, but they are no longer available. The website is great for RV electronics, though it is terrible to navigate.

I'm sorry to hear that Joel Donaldson, the owner of LSL Products, karked recently. He helped me with my installation, and from his emails I found him to be approachable and very knowledgeable. I hope that his estate can sell his business to someone else who can resume making his products.

John