Battery Charger

SWharton · May 7, 2019

Since switching to AGM batteries we now realize we need a new battery charger(for backup). We are looking at this one:

https://www.amazon.com/NOCO-G3500-UltraSafe-Battery-Charger/dp/B004LWVEKS/ref=sr_1_2?keywords=noco+3500&qid=1557233714&s=gateway&sr=8-2

We are lost in the world of technology change. Our old battery charger has 2 options 2 amp and 15 amp. Will this one be adequate? Don't know if it matters but we have 4 AGM house batteries.

Thanks,

oldjohnt · May 7, 2019

Sure, the charger you posted will pump some (albeit low only 3.5 amps, would take a longggggg time to replenish if much discharged ) charge into your batteries HOWEVER I view your selection more of a battery maintainer or trickle charger then any serious RV charger if you have a substantial battery bank such as say 200 to 400 Amp hours and you dry camped and they become say 40% discharged. With 4 AGM batteries, although I don't know your total Amp Hour Capacity, if you dry camped very long, Id venture a pure "guess" more like a 30 to 50 amp or more AGM compatible charger may be in order once you're on shore power. As an example, I'm running 520 Amp Hours of AGM batteries, might discharge say 150 Amp Hours worth, and have an 80 Amp PD 9280 Smart 4 Stage Charger which is more then needed.

If you dry camped for some period and lets say you used up 100 Amp Hours of stored battery energy, so you got plugged up and wanted to bring your batteries back up to 100% SOC, at 3.5 charging amps it would take (in simple but inaccurate terms) 100/3.5 = 28.57 hours HOWEVER it takes much longer due to battery chemistry and loses etc. If you had say even a 30 amp charger you see how much shorter the time to get charged back up. Of course, if you only became say 30 Amp Hours discharged a lower amp charger can get you by.

Its also a matter of your budget, but a 3.5 amp trickle charger maintainer isn't what id consider a serious charger IFFFFFFFFF you need to replenish very many amp hours over a reasonable time. If time to recharge isn't an issue a low amp charger can get you by.

John T NOTE not knowing your battery capacity and degree of discharge and time to recharge, the above can only represent a pure inaccurate guess, sorry

Darryl&Rita · May 7, 2019

At the link you posted, the selection only goes up to 26 amps. Noco makes a good maintainer, but no real chargers.

hemsteadc · May 9, 2019

No, it won't be adequate. You need something in at least the 60 amp range.

SWharton · May 9, 2019

NOCO suggested the 26000(26 a) which is way too little we think for how we might need to use it. We didn' realize 3.5 was its "full" output. We thought that was the trickle number. Our old one is 2(trickle) and 15. Learning curve.

We were thinking 75-85 amps. We will keep looking and learning. It is not on our critical path.

Tom_M · May 14, 2019

A better option would be to purchase a converter and add cables to make it portable. To make it future proof, you may consider one that is adjustable and rated for lithium. You can check BestConverter.com which has many choices.

SWharton · May 14, 2019

Good idea, we will look into it.

oldjohnt · May 14, 2019

On ‎5‎/‎9‎/‎2019 at 5:50 PM, SWharton said:

We were thinking 75-85 amps. We will keep looking and learning.

I'm running a Progressive Dynamics PD 9280 I believe, which being an 80 amp is in the range you mentioned. It has performed great and there are several other quality brands to choose from. These aren't "cheap" but you get what you pay for and if they extend battery life it makes them worthwhile.

John T

Sehc · May 14, 2019

This article is about marine chargers, but it is relevant. https://marinehowto.com/installing-a-marine-battery-charger/

Here is one about your AGM batteries. https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

Al F · May 19, 2019

On 5/14/2019 at 10:38 AM, Sehc said:

This article is about marine chargers, but it is relevant. https://marinehowto.com/installing-a-marine-battery-charger/

Here is one about your AGM batteries. https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

I found the second link: https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/ to be extremely beneficial to read.

Great detail on exactly why you can't charge a battery from 50% SOC to 100% in just a couple of hours.

It is a very technical write up, but a must read for anyone dry camping or boondocking for more than just a few days in a week or any period of time before connecting back to shore power for an extended period.

Bottom line, it takes at least 5 or probably many more hours of charging to get the battery from 50% SOC to 100%. Depending on your charger, it may take 8-12 hours to charge the battery to 100%.

The article confirms, with extensive detail, what I have read about battery charging for the last 12 years.

SWharton · May 19, 2019

Thanks for all the info. For now, we are deferring buying a new charger until we are in winter camp so we have time to study our options. Needing a new charger was just something that we realized we needed with 5 AGM batteries. Our rig is working fine with our 4 solar panels and generator. This is just something that occurred to us and we realized technology had changed dramatically since our last purchase. Thanks for all the info and input.