Best Solar Backup System

[captnredbeerd]

A lot of jargon up here that I don't totally understand, and maybe I'm missing the mark... but bringing it down very simple.. I use a battery trickle charger to top off my battery bank when its getting low d/t short or cloudy days. when i'm parked with shore power i plug it into that. you could also run it off of your engine starting batteries if you were idling, but keep in mind you're alternator is not putting out much amperage when idling, so keep an eye on your engine battery voltage. if you're actively driving you'd be totally fine. a third option is a cheap low wattage generator. the trickle charger only draws low power, so even the smallest genny should provide plenty of power.

[john61ct]

Most devices called trickle chargers are not suitable for properly caring for a deep cycling bank.

Higher amps are likely needed.

Secondly anything old-school automotive rarely has the accuracy, adjustable flexibility and "intelligence" (stages) required to match the mfg specified needs,

obviously both aspects depending on chemistry type and Ah capacity of the target bank.

[rffffffff]

To get back to the beginning, I think In your circumstance an iota charger would work well. I have one and it’s been super solid. They have different modules you can plug in for different battery types and they’re not stupid expensive, but also not the cheapest option. I love mine, it’s a 55a version, does the job for 800ah of lead acid with my little Honda generator when I’m off grid.

[Welshie]

I'm just finishing my build and am planning on living in the high rockies in CO. I bought a battery to battery charger from Sterling Power. Not tested it yet but research showed it to be good. It does seem like it needs to be used whilst the vehicle is in transit though as it only draws power from the alternator once the vehicles battery bank is full.

[john61ct]

That last is completely false.

But yes, the intention is for it to only be used while fed by an active power source (not necessarily an alternator)

It **could** be used to transfer stored energy from one bank to another but that would be stupidly wasteful in most circumstances.

[Jsneeb]

Ok, I think we got way off track to your original question.

Im in the same situation, though I have 990W of solar and 3.5kw battery.
Winter solar hours, full time in the bus, regularly running appliances, etc I find myself sometimes in the same posittion.

What has worked for me is to rely just on two things.

1:
Isolator relay and Dc-Dc link for my house battieres.
If i drive the bus I can see 20A & 24vdc going into the batteries.
This recharges my system up by 50% after 4-5 hours on the road.

2:
Shore power.
When I know its going to be cloudy, and cold for the next several days. I will find somewhere I can plug into shore power overnight.
If I find somewhere to plug in ( campgound, rv park, picnic area outlet, exterior of some building, parking lot where the street lights have an outlet behind the screwed on cover, etc.) then I can manage to just top up using shore power overnight and be good for a while.

You mentioned you would need to use this once or twice a month...

Between driving somewhere once a month, and finding shore power once a month you got your problem resolved. Try that.

I don't have a generator, or anything like that, If I needed it regularly I would use it. but for me having the shore power connections works out perfect when I need it.