Connecting panel and appliance to battery gator clamps

[hippyhunter]

Am thinking about a projecta 120w solar panel and a fridge to use with my 100ah lifepo4 battery. This solar panel has an inbuilt controller and uses alligator clamps to connect to the battery. The fridge will obviously also have alligator clamps. If i attatch the solar panel to the battery then just clamp the fridge clamps over the top of that is that acceptable or will that be bad for battery and/or fridge? The lifepo4 battery has a bms built in also.
Ive tried google but cant seem to find an answer in regard to alligator clamp piggy backing. Im 50/50 on this as being either fine, or a disaster.
Cheers

 

[Ridge Runner]

Am thinking about a projecta 120w solar panel and a fridge to use with my 100ah lifepo4 battery. This solar panel has an inbuilt controller and uses alligator clamps to connect to the battery. The fridge will obviously also have alligator clamps. If i attatch the solar panel to the battery then just clamp the fridge clamps over the top of that is that acceptable or will that be bad for battery and/or fridge? The lifepo4 battery has a bms built in also.
Ive tried google but cant seem to find an answer in regard to alligator clamp piggy backing. Im 50/50 on this as being either fine, or a disaster.
Cheers

The chances are your panel has a PWM Controller so it won't be quite as good as an MPPT but sure you can do that, It just won't be pretty, Other than that it should work fine, :Y:

 

[hippyhunter]

Thanks rr. I should be able to wind the posts out longer on the battery so each clamp has its own estate on the battery post. I think i might even look at cutting the alligator clamps off and use ring terminals so can still have room for charging the detector.
Thanks again. Hope all is well up your way.

 

[hippyhunter]

Decided against that panel in the end. I get the feeling that controller will ruin the lithium battery with its float charge eventually..

 

[Ridge Runner]

No worrie's,

Thing is Your panel is made to be used exactly as you discribe, hense the Crocodile clips along with other connectors that they come with etc, I bought 2 of the Eco-worthy 120w Panels and gave one to my Brother because we both use them the same way as you as well as charging Deep cycle batteries,

Seeing as you are using a 100Ah Lithium battery you might want to consider getting another matching panel and link the 2 because some of the bigger Lithium Batteries demand a higher charge rate, A 120w panel works well on my 40Ah/512Wh Lithium Porta Packs as it will yours but if your power demands go up drawing more from the Battery then maybe you might want to look in to adding another panel, But first off don't rush out and spend more money just yet, Give it a trial run and if all is good then leave it as it is,

One thing for sure Lithium batteries will suck up all the power your panel can put out so you won't be wasting power or Time like you do with Deep Cycle batteries,

I am doing good, It's 4*c here right now, was 1*c a couple of nights ago, went camping last week and the Lithium packs really work in these conditions so you should Ace It,

hope that helps, Take care.

RR.

 

[OzzieAu]

Why not just wire a Anderson plug across your battery posts and use one of these to connect multiple input/outputs.

It would mean cutting all the alligator clips off your cables and connecting anderson plugs.
Much safer and convenient.

 

[Jaros]

That's what I've done Ozzie-works well with different power inputs/outputs.

 

[condor22]

The biggest issue charging a LiFePo4 from solar is voltage!

First thing in the morning or on a really overcast day, the panel/s output voltage may not reach the minimum voltage required to charge. Yes, the battery has an internal BMS which regulates the battery's charge/discharge. Protecting the battery from over discharge and over charging are it's primary function.

So, if you are all connected up with solar going in and fridge drawing power out, you won't really know the state of charge (SOC) without a battery monitor, which measures power in and out, then calculates the net SOC.

Unlike an AGM, a Lithium has a relatively constant voltage between approx. 10% SOC and 90% SOC, so a simple voltmeter won't be of much use until your battery is getting pretty low.

A few Lithium batteries have a LED indicator that has 4 lights showing 100%, 75%, 50% and 25% SOC. Even that is only a guide, but better than nothing.

Bottom line, know what you are using (fridge) and replacing (solar) and keep tabs - More solar is better than just enough - MPPT will maximise voltage, PWM won't.

 

[condor22]

Forgot to mention, we all know the term BMS, however it has 2 connotations.

For years re AGM etc it meant Battery Monitoring System.

Now with Lithium it can mean Battery Management System.

The 2 are totally different in application, lol.

 

[hippyhunter]

Thanks guys. I havent actually purchased a panel yet, was just eying one off cos it was going cheap, so thought i better get some more info first... luckily.
I have the battery already which has a bms with a digital voltage meter/gauge built in. So that part will be helpfull.
Im pretty sold on a 25l brass monkey fridge, so just need to figure out a panel and connections. Kind of have a dislike of anderson plugs from forklifts and smashing my hand on cold mornings unplugging the *******s. Still do look better than allogator clamps though.
Was only eying off the projecta one iminently as it was very cheap. Glad i asked questions first. All good. Means i get to do more window shopping

 

[Ridge Runner]

Thanks guys. I havent actually purchased a panel yet, was just eying one off cos it was going cheap, so thought i better get some more info first... luckily.
I have the battery already which has a bms with a digital voltage meter/gauge built in. So that part will be helpfull.
Im pretty sold on a 25l brass monkey fridge, so just need to figure out a panel and connections. Kind of have a dislike of anderson plugs from forklifts and smashing my hand on cold mornings unplugging the *******s. Still do look better than allogator clamps though.
Was only eying off the projecta one iminently as it was very cheap. Glad i asked questions first. All good. Means i get to do more window shopping

Not heard a bad word about the BM 25L, Seems to be the best one on the market to date, erfect:

Glad Condor cleared that up, Lithiums do like peak voltage, Even my PLB's ( 40Ah ) Dometic say around 8 to 10Ah which is 20 - 25% of the battery rating, So I would imagine yours would require a minimum of around the same % of input just to keep in front of the fridge and still manage to put some back in the battery at the same time, Due to the weather here is why the best I can manage is 2X 40Ah where I can swap them out where as a single 80 or 100Ah would leave me Begging. 8.( 8.( 8.( :brokenh:

 

[woomera]

LiFePO4 State Of Charge, Voltage Chart

 

[user 20746]

My experience is that the MPPT charge controllers are far and away better than the old PWM, I have two identical FLA banks side by side using mppt and pwm and the mppt compared to the pwm is very noticeable, lithium likes voltage and the bigger you go on the panel the better, depending on the circumstances/space you can use house panels (I picked up 2.5kw worth of panels for $300) and as other have said use the anderson plug set up, it is easy, neat and foolproof.....as an aside I dont think I have ever seen a pwm charge controller be able to charge a lithium battery but I could be wrong.

 

[condor22]

One of the reasons voltage is not an accurate indication is; Here are 3 different scenarios with an AGM

1. Battery fully charged and at rest for some time = 12.9 V approx.
2. Battery, fully charged and with a 3 amp fridge load, the voltage drops to around 12.6 - 12.7 depending on the ambient temperature, battery age and condition. As the battery discharges the voltage will continue to drop. I've seen a fully charged older battery go to around 12.3V under the same load.
3. Battery fully charged, under the same 3 amp load and at the same time being charged from a 200W MPPT system. In good sun conditions the voltage can exceed 14V. Plus, if the battery was say at 50% SOC, then the voltage will still be up at 14+V, because the panels are holding the voltage up.

LiFePo4 batteries are not as affected by loads in the order of the above fridge 3 amp load. My Pylontech when full drops around 0.1V under a 3 amp load. The higher the load the lower the voltage drops.

There is a narrower voltage range of a Lithium compared to an AGM re SOC. For either type of battery - voltage can only be a guide if, you disconnect all loads and charging, let it rest for a couple of hours then put a voltmeter across the terminals in around a 20-25C ambient temp. Which in the real world rarely happens, cos your running a fridge and don't want it off, lol.

I'm using the Projecta BM320 on my lithium. It's not specific for lithium, especially re voltage. However, it measures the current going in and the loads going out across the shunt to calculate the net SOC. (temporary fix until I revisit the van as it's mothballed at the moment.)