Need Help, Ongoing Power Problem After Being Fine For 2 Months

So I purchased a mostly converted short blue school bus 3 months ago. It had 4 interstate costco batteries 6v golfcart 210AH each for a total of 420 AH at 12V. I had it connected to a 2000 Watt microsolar inverter and that to my electronic system which normally sits between 60 and 120watts, occasionally going up to 240 watts for brief periods of time. This was connected to solar controllar I believe from Renology which is hooked up to 400 watt solar panels. This worked GREAT for a month. The batteries lasted up to 2 days when cloudy and getting no charge from the sun.

Eventually the batteries died due to me not knowing I needed to water them. I got new ones and hooked up a battery monitor when I installed them. Everything appeared to work fine for awhile. The battery monitor never dropped below 12.1V with load on.

Then one week it was very rainy and my batteries dropped pretty low 11.4V and I went to an RV park to charge the batteries. I hooked up my battery charger to the RV park AC and charged the batteries overnight. After that the batteries seemed cooked, after only 20-40 AH they would drop down to 11.4V effectively dead. I figured perhaps I had overcharged them so I went and got them replaced with 4 more NEW costco interstate 6v 210AH golf cart batteries.

When I hooked these up, they where showing 12.3 volts so I figured they just needed to charge up to full. (I also checked them before I installed and they read 6.15V each). I charged them up to full with solar. That night, first of all they immediatly go down to 11.8 so I know something is up. I am thinking perhaps the problem is my invereter, so I replace the 2000watt inverter with a brand new 1000watt renology inverter. Now the batteries go down to 12V immediately under load after supposedly being full. Then after only using 50 AH the batteries again die, go down to 11.6 volts (I just call it quits here this time since I do not want to damage the batteries and I have read that is a good stopping voltage for golf cart batteries.).

So what I am asking is, what on earth could be going on? It seems highly unlikely that the new batteries are bad. But why on earth are my batteries dying so fast? I am hitting them with the same load as before, and I have manually calculated my supposed wattage and it matches up with what is being displayed by my battery monitor. I have also used a voltmeter to check that my battery monitor is accurate, and the beeps from my inverter seem to agree. What can I try to debug this? Is it possible that these “new” costco batteries are just bad?

Greetings & Welcome!

Your problem is likely two fold, not enough solar, and lack of additional and better charging methods.

The days are getting shorter, less daylight hours means less solar energy, and they’re not going to get any longer for months. Full timers suggest 3+ times the amount of solar you have for that battery storage. People who claim to be happy with their solar, also typically have an isolator & a generator to take up the slack, and give the solar more credit than it deserves.

Like so many other people, I’ve ditched solar in favor of an isolator that takes care of my needs 99% of the time. I have a cheap ($99) generator & a cheap battery charger to take care of things when necessary.

One solar boondocker I know has a 32’ rig with the roof covered in solar panels, and still puts out another 1200 watts of solar on the ground aimed at the sun, and still needs to run his generator almost every day to top off his 800 amp battery bank that cost him over $8k for the lithium batteries, which he is on the second set of in under 5 years.

I’m cheap, not because I’m forced to be, but because I understand that everything can be gone instantly. Car thieves, fires, explosions, wrecks, you name it, we’re vulnerable. We also can’t count on insurance companies either. These are just a few of the reasons that I try to keep everything as cheap as possible. My real insurance is my emergency fund, with which I can replace or repair anything almost instantly, including my whole rig and all my belongings.

Being cheap doesn’t mean we need to compromise on comfort or convenience, only that we need to make wiser choices.

I just checked Harbor Freight, and they have a 900 watt gas generator on sale for $109. It probably won’t run a microwave or an air conditioner, but it’ll run a battery charger just fine.

They have a relatively cheap battery charger if you need it too.


"Don't be scared, BE PREPARED!" ~ Road Warrior

now thats what you call a reply you should be reclassified as am emergency service

hope the op took notice hahah

1 Like

What kind of battery monitor are you using? Does it display amps in and out?

Battery voltage is not a good indicator of actual battery life. There are a lot of variables involved there. Typically you’d need a battery to set for at least a few hours before measuring them with a meter to get their actual voltage. 24 hours ideally. So unless you’re taking the decay into consideration they may not actually be full when you think they are.

Check the date on the batteries as well. Unsealed lead acid batteries don’t store as well as AGM’s and others do. I would wonder if Costco maintains them at all after they put them on the shelf.

You could always takes them to autozone and have them test the batteries. I’m not certain but, I believe one bad one could ruin the entire batch.