8 replies to this topic

[UmkaAndHawk]

I'm considering the Zamp ZS-30AD 30A which can charge two different batteries. Now my current setup will have two identical AGM batteries, but would this allow me to upgrade more slowly to one Lithium battery at time? Is it worth it? 

 

Also, is this solar controller also a replacement for Victron voltage monitor BMV712 or no?

 

Why Zamp or why not Zamp? Any thoughts welcome!

Edited by UmkaAndHawk, 11 January 2021 - 04:49 PM.

[longhorn1]

I don't believe you can have one AGM and one Lithium. Batteries should be the same. The solar controller needs to be compatible with lithium. Some aren't.

[rando]

Unfortunately the answers are no, no and no.    

 

While that charger could charge two different battery types, they would need to be separated for charging.   You also don't want to put an AGM in parallel for discharging as the AGM would not do anything due to the lower resting voltage (all the current would come from the lithium battery).   So in short the only way this would work would be to have two entirely separate house battery banks, which would be unwieldy.  If the two AGM batteries (presumably ~75Ah each) work OK for you, then you will likely only need one LiFePO4 battery anyway.

 

This will not replace the functionality of a BMV-712 as it doesn't measure the load current side of the equation. 

 

As to ZAMP in general, my highly subjective opinion is that they are meh.   Nothing wrong with them, and they do provide good US support,  but older technology and not very well designed products for a fairly premium price. 

[Wallowa]

Umka,

 

Newbie here...but Zamp Controller is a PWM [unless they have changed] and Victron, for example, is a MPPT type controller... and they are two different means of metering and 'controlling' solar input...from what I have learned MPPT has the edge on efficiency ...my '16 Hawk FWC Zamp is a PWM and does not have lithium capacity...newer Zamp Controllers can support LiFePo4 batteries.

 

I added a Victron BMV 712 mostly to have an accurate monitor of the batteries [currently [no joke intended..] two 75AH AGMs] 'state of charge' [SOC] or how much juice do I have left....my Zamp only guesses at the SOC based on the voltage. 

 

Many on this forum with a lot of knowledge and they will share it...me, I am just learning...so "trust with verification" what I say..

 

Phil

Edited by Wallowa, 11 January 2021 - 08:09 PM.

[BrianG]

Even with lithium you must have batteries that match, for example 2 100ah, but a 100ah + a 50ah will not work together. Battleborn recently explained this to me. 

[Keith in Co]

I went with a Renogy DCC50s which is both an MPPT controller and a DC/DC battery charger in one package. Once it changes my 100ah lithium house battery to 100%, it charges the dual lead acid truck batteries in my Dodge diesel. It will charge any type of battery, but as noted by others here, you have to use the same type and size batteries on any one circuit. I have three, 100w solar panels. Works well.

https://www.renogy.c...campaign=760144

 

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[UmkaAndHawk]

Thanks everyone for the clear answers. I have a follow on question, I'm surprised I haven't found the answer to yet:

 

I have the East Penn Initimidator 8a24m battery (that came standard in the FWC hawk shell). Starting with using just a voltage measurement, and supposing nothing is on, that is, everything is still connected, but all the lights are off, and the furnace is off (but the CO monitor is still connected...that's all that's in my shell...) what's the lowest voltage I should go for 50% depth of discharge? 

 

I couldn't find a curve anywhere on East Penn's site to indicate no (or quite low) load voltage as a function of depth of discharge. Anyone have this? Does it change for two batteries in parallel (it shouldn't, I think).

 

Note: let's assume around 72°...if anyone can add how that curve goes down with low temperatures, all the better.

 

Thanks!

Edited by UmkaAndHawk, 23 January 2021 - 04:58 AM.

[Vic Harder]

Voltage is a lousy way to determine SOC, but... 

How to Troubleshoot Deep Cycle Battery Issues (aussiebatteries.com.au)

[rando]

Vic is right that battery voltage is only somewhat useful for determining State Of Charge (SOC) for a battery when it is being used, but is OK if you want a rough idea when you know nothing is running and the sun has set.  

 

In this situation, I would ignore the 50% 'rule' (which is not a rule and is not even a good suggestion in many situations),  and not be afraid to take your battery down to 80% - 90% Depth of Discharge (DOD).   

 

Below is a typical cycle-life vs depth of discharge curve for a deep cycle AGM battery.    Taking the battery down to 80% (or even further) would still yield ~300 - 500 cycles, which is a LOT of nights out for a weekend warrior.   In our campers, weight is a big issue, so not carrying around twice the battery capacity, and only using half of it does not make much sense.   It also sounds like you are already considering upgrading to LiFePO4 batteries, so getting 6+ years of service from your batteries is probably not your goal. 

 

Based on a 80% DOD, you would want to limit your use below about 11.7 - 11.8V based on the chart Vic provided.

 

Source: https://offgridham.c.../agm-batteries/

Edited by rando, 23 January 2021 - 05:57 PM.