Wiring off or Batteries Bad ?

[jogi4114]

I have a 500 watt system on my toy hauler with a 4 6volt battery system wired for a 12volt system but It seems like I am only getting around 100 amps in total once charged. Each 6 volt battery is rated at 225 amp hours. Im not sure what is going on. Can somebody please shed some light on what might be the problem. The mppt charge controller seems to be working and blinks full everyday but at night again it seems as if I only get around 100 amp hours. Thank you for your help

[littleharbor]

How old are the batteries? Have they been maintained properly? Equalized when needed? Your symptoms sound like your batteries are old and in need of replacement. Have you checked specific gravity with a hydrometer?
500 watts of panels on a flat roof wont come close to the 40 - 45 amps needed to fully charge your battery bank. Is your controller a real MPPT ? There are many fake so called MPPT controllers.

[jogi4114]

I bought them about 2 years ago and I have drained them a few times but I was told (vmaxtank) batteries can handle discharges like this once in a while. They are AGM so I not sure if I need to check them like you mentioned. The MPPT is legit, its from Renology. I do have an old inverter built in that came on the toy hauler which the solar installer told me that he installed a bypass switch so it would not work against the new inverter that I bought for the system. I just feel since the first day I never go anywhere close to Im guessing 450 amp hours total or even 900 amp given the fact that there 225 amp per battery. Im just trying to figure out some answers because they drain pretty quick.

[SunEagle]

What I see is a typical problem caused by wiring batteries in parallel and over discharging them a few times. That is a recipe for an early death of one or more batteries in the system.

[littleharbor]

If wired up at 12 volts you have 450 ah of which 225 is about the usable limit, 50% discharge. You don't want to discharge down to 50% too often. 20 to 25% is all you really want to draw on a regular daily basis.

[ewarnerusa]

How have you determined that you only seem to get around 100 Ah out of your battery system?

[Sunking]

Educated guess 1 of 3 things is going on. Most likely a combination of all 3.

1. Peukert Law which states change in capacity of rechargeable lead acid batteries decreases as discharge rate is increased. Batteries are rated at the 20 hour discharge rate. That means 11.2 5 amps for 20 hours. If you discharge at 50 amps the battery is now a 150 AH battery. At 83 amps is a 83 AH battery.

2. Abused or old batteries. Or perhaps you do not know how to measure Amp Hours.

3. Poor workmanship wiring the batteries.