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So after a long power outage (> 8 hours) it appears that the battery for my backup sump pump has died and I want to replace it.

I have a Basement Sentry I, Model 507 by Zoeller

The manual recommends:

  • DC, 12v
  • Deep-cycle 12 volt, 105 amp-hour marine battery
  • Battery with top terminals
  • Battery size no larger than: 13.5l, 7w, 9.5h

I found this:

https://www.lowes.com/pd/Zoeller-Basement-Sentry-Battery-75-Amp/5000050333

It doesn't have the 105 recommended amps, but would something like this be inline with what I need?

Or something like this:

https://www.sumppumpsdirect.com/Interstate-Batteries-DCM0100/p50877.html

Also, would changing it be akin to swapping a battery for a car?

Any insight would be helpful.

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    How old is the battery? 3-6 years is expected life of lead-acid, but they're so cheap who cares. Yes, I know they seem expensive when that's the only battery you've ever priced lol, but try a long-life battery like NiFe or lithium. However, don't let anyone surcharge you for a special magic "sump pump battery". Any deep cycle battery will do, see standard battery sizes. shop.advanceautoparts.com/r/advice/car-maintenance/… Feb 29 at 21:23
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    Also check at your typical auto parts stores, as they may have deep-cycle marine batteries at a better price than other places. Take in your old battery and you can typically get a "core" refund for returning your old battery. Or what they'll often let you do is return the old battery within a certain period of time (a few days typically) for that core refund if you don't want to leave your system battery-less while you do the new battery purchase.
    – Milwrdfan
    Feb 29 at 21:41
  • Shopping is off-topic, so I'll just comment: If there is one near you, try Batteries Plus: batteriesplus.com/battery/marine-and-boat/… I use them regularly for UPS batteries and sometimes other stuff. The key is that if you find a local place that deals with a lot of batteries then you can often do much better than order-online because you then either have to pay for shipping (batteries are heavy!) or "free shipping" builds it into the cost. As others have suggested, marine, auto (but more specialty), RV, etc. places may be good too. Feb 29 at 23:39

3 Answers 3

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Whether you buy a battery with a lower Amp-hour rating is up to you. The recommendation given is so that the pump can run for what the manufacturer considers a reasonable amount of time. It won't affect performance other than cycle duration.

The physical dimensions and top-terminal requirement are logistical parameters--if you want to get a different drybox and longer cables (or suitable extensions), use whatever 12v deep cycle battery you like.

Changing the battery is indeed like changing a car battery (or marine battery). The danger is not to you via skin conduction, but in the potential for short-circuit through metal tools, etc., which results in high-current arcing (and often welding). Keep the positive cover in place until the battery is secured in its location and the negative terminal is connected. This reduces the chance of inadvertent contact. Snug everything well, but don't overdo it.

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This might be a good use case for a LiFePo4 battery. They can work as 12V drop in replacements with no changes to charging, do thousands of cycles if needed, float well for years, and last for a decade+, often at similar cost per Wh to an AGM.

The only critical attributes are size (if you want to use the battery box) and connection type (if you don't want to change the wire ends). Otherwise I'd expect any AGM or LiFePo4 battery 50Ah+ to work well in this sort of application. Don't use a LiFePo4 if it could be subject to freezing.

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    So no good for a car battery in Canada/Northern States?
    – crip659
    Feb 29 at 22:56
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    Not unless it has a heater. Some of them have a heater built in. They can discharge below freezing, but it damages them to charge them with the battery that cold.
    – KMJ
    Mar 1 at 4:05
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    I have Lithium batteries in two of my motorcycles. I'm not sure I'd trust them for this. They kick out at a certain (fairly high) voltage, whereas a Lead battery will keep going as long as it can turn the pump. That's a desirable feature in an emergency.
    – isherwood
    Mar 1 at 13:39
  • If your LFP batteries are decent, you'll find that total energy delivered between the start of use and when it drops out is the same as on the label. Meanwhile your Pb battery will output less total energy if it's used at a higher rate. And if you run it all the way down to low voltage for some reason, you'll only get a few cycles out of it before it's toast. They have their limits of course, but generally LFP batteries are superior if you care about lifespan or actually being able to use the energy stored in the battery.
    – KMJ
    Mar 1 at 21:33
  • Also the difference between cutting off at a reasonable voltage and cutting off at totally dead on an AGM is not much time. centennialbatteries.com/amfile/file/download/file/164/product/… is a data sheet for a 105Ah AGM, and it will be fairly typical. You can extract from that info that the 6 hours of runtime Zoeller quotes will be about 30 minutes more if you run the battery down to a voltage low enough to do serious damage to it.
    – KMJ
    Mar 1 at 21:45
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Take it to walmart and have the auto people do a load test.

If it doesn't pass then get a 75Ah deep cycle battery there. I got a group 65 one for my PumpSpy 1500W Sump Pump Battery Backup System. $30 cheaper than the lowes one.

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  • You're suggesting specific products here without much reasoning to support the recommendation. A 20 Ah drop from spec is quite a bit.
    – isherwood
    Mar 1 at 13:41
  • That was just a comparison to the 75Ah deep cycle linked from lowes. You are correct I'd stick to the spec and get a 105Ah battery. Mar 1 at 17:17

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