Hi! I have an already converted van, which has 2 AGM lead-acid batteries in good condition. I want to add more AH to my pack, but I am not interested to invest in converting everything to lithium for this van that I won’t keep for very long still. I am looking into adding 1 or 2 used AGM batteries. Are there any rules to follow in terms of choosing the batteries that will be added? Same brand and technology (AGM) of course, but anything else?
Should the total AH of each battery be the same or similar?
Is there a limit in the number of lead-acid batteries we can add in parallel?
Thanks!
Greetings & Welcome!
Adding additional deep cycle batteries shouldn’t be a problem, but you might be asking the wrong question…
You didn’t mention your battery capacities, charging methods & capacities, or your usage.
More often than needing more batteries, people need more charging.
Cheers!
"Tough people thrive in tough times." ~ Local Yocal
Yes thank you! I have 2 75 AH AGM batteries charged by solar and through the alternator, 2000W inverter. I think this is a little below our needs (fridge, LED lights, electric water pump, phone/computer charging). We are travelling in long stretches around 2 months at a time, relatively off-grid. This is why I was thinking off adding more similar batteries. Thanks!
Greetings!
How much solar do you have, and what are you using the inverter for? That’s a very large inverter for your battery capacity.
You can easily add more batteries in parallel, but what we need to figure out is how we’re going to successfully charge them. So we need to know how much solar you have, and what charge controller you have. Your charge controller may not be capable of adding more solar panels, so it may need to replaced too.
What is your setup for charging while driving, and how much driving are you planning on doing? Charging while driving is more effective & more reliable than solar, but doesn’t help much when you’re stopped to smell the roses, and of course that’s a large part of what road trips are all about.
We also need to consider where you’re traveling, and how effective solar will actually be in those travels. I’m also always off grid, so my simple solution is a gas generator and a normal plug in battery charger. Rain or shine, my generator can always provide me with all the power I need. Some people will pay for a campground with electricity for when they need to charge their batteries, but I prefer to be self sufficient.
Once we figure out exactly what you need, I would weigh the costs vs. benefits of the various options, before proceeding.
Cheers!
"Tough people thrive in tough times." ~ Local Yocal
Hi! Thanks so much for your time!
I have 200W of solar panels linked into the Epever MPPT tracer 30A (Tracer3210AN) controller
Greetings!
I think I would try doubling your solar before anything else. If that doesn’t work, then you’ll need more batteries, more solar, and a bigger charge controller.
You currently have approx. 75 amps of usable battery capacity. If you’re using it all daily, you’ll need to replace 115 amps back into it for a full charge. With 400w of solar, that’s 5+ hours of sunlight minimum per day. Depending on the charging capacity of your batteries, it could require up to 8 hours for a full recharge.
5 hours in the winter can be difficult, and 8 hours is practically impossible.
Your alternator will put out very little at idle, much more while actually driving. But we can improve the alternator output by either idling faster, or changing the pulley sizes to double or even triple the RPM of the alternator at idle speeds. A second high output alternator is another option.
In a pinch, in towns, some auto parts stores will charge batteries for free too.
Cheers!
"Tough people thrive in tough times." ~ Local Yocal
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Thanks! That is good insight! We only use the van in the summer and we drive a lot (1-3 hours/day on average). In that case, would just adding the batteries without doing all the other modifications be beneficial? Again, I probably won’t keep this van for very long so I want to limit the investments if possible. Thanks!
Greetings!
I suspect that you’re suffering from under charging, more than lack of battery capacity. If it was me, I’d start by tripling my solar to 600w and see if that doesn’t solve all your problems.
Cheers!
"Tough people thrive in tough times." ~ Local Yocal
It is not recommended to mix old and new batteries in the same battery bank. You should build a battery bank from new, identical batteries.