Reddit reviews 12v 200AH 4D Deep Cycle Replacement SLA/AGM Battery - 2 Year Warranty

Thank you!! We have 600 watts of solar on the roof (which is an obscene amount) and two 200 amp hour sealed lead acid batteries (these guys). Here's the inverter we have.. We basically have standard household appliances: we occasionally use a microwave, we have a toaster, and we have a regular cheapo minifridge. We chose to use our big ol' roof and some space for batteries rather than worrying too much about having the most efficient fridge. Most of the time, though, the solar powers our lights, laptops, and fridge. If you're curious, we found this book very helpful. It's very practical and easy to understand.

As far as the off-grid length:if the batteries have been fully charged on a regular basis, we can live our regular lives (using lights/plugging in laptops) for about three days with little to no sun. If we have good sun, the limiting factor is water. We have 80 gallons of water, and we've found between drinking, eating, washing dishes, and very occasionally ourselves, we can last about two weeks without refilling.

Deep cycle batteries such as AGM or lead acid do not like high discharge rates. Sealed lead acid and AGM do not have to be vented or refilled with distilled water, they are much less tolerant of heat than regular lead acid deep cycle batteries though (which MUST be vented).

Life cycle is how many times can you discharge and recharge a battery and it still be worth a shit. This is the first hard truth in batteries....the more you use it for its purpose the less you can use it. All batteries can only be discharged and recharged so many times no matter how ideal you make the conditions.

AGM...acid glass mat... can be discharged maybe 500 to 750 times IF you only discharge them 50%. I bring up this 50% number because I feel thats a reasonable balance between use and longevity.

A 200 ah AGM battery is $330 delivered with a 2 year guarantee.

Lithium Ion can be discharged to 50% and recharged 2500 times. (they can be discharged much further but the same as AGM the more you discharge the less lifecycles you get) If you only discharge 10% and recharge then this can up to 10,000 times. Its ridiculous!

A 200 ah Lithium Ion battery can cost over $1000. this one is $2000 so you really have to shop around or here is one sort of for $800 You really have to shop around with Lithium Ion. I think these are considered something of the gold standard and 200 ah is going to be $2000 again.

The other consideration is charge and temperature.

Lithium Ion HATE being fully charged and being hot. The battery experts recommend keeping a Lithium Ion battery at about 65% charge and they recommend not to store them above 86 degrees F. Keeping a Li-ion battery fully charged (according to them at least) reduces its number of lifecycles to almost an AGM. This is very bad cost effectiveness because increased lifecycles is what youre paying for with a Li-ion.

The site I linked says that at 65% charge you can squeeze out up to 4000 lifecycles (which is 6 to 8x more than an AGM)....but this presents an interesting "squeeze". If you charge more than 65% you lose life cycles but if you discharge more than 50% you also lose lifecycles, yet using just 15% of your batteries capacity means youre going to really need an expansive battery bank.

So thats the consideration.... lifecycles vs cost. If you pay 6x more for a lithium ion battery than an AGM then you need 6x more discharge cycles to get your money's worth and you need to read up on how to make sure you get it.

I went with AGM because I didnt want to do that. I wanted to hook my batteries up to my solar panels, have them charge up to 100% and I didnt want to give them a second thought.

I've bought a few of these 200AH AGM deep cycle 4D batteries and am perfectly pleased so far. They are far far cheaper than comparable batteries I've found. The down side to the big 4D batteries is that they're quite heavy, and if you expect to be moving it around a lot maybe not a great idea. The 6v in series vs 12v is a lively debate, but what we know for sure is that deep cycle AGM batteries will give you the best possible performance and last much longer.