Inverter voltage drop when using.

 
Motorhome Craic sponsored by
 
 
 
 
 
mvnube
Craic'er
Avatar
Gender:
Location: Kilkenny City, RoI
Age: 74
Posts: 24
Registered: 07 / 2018
My Motorhome: Rapido 990M called "Rose"
Base Vehicle: Sprinter 7.4m
Subject:

Inverter voltage drop when using.

 ·  Posted: 30.04.2022  ·  #1
I have just bought and test rigged up a new 3000Kw pure sine wave inverter in my MoHo. I connected it up to my 3 x 115AH leasure bateries, battery age unknown. Using 25mm2 x 2m cables to the inverter.
Voltage without any load shows 13.5 volts.
When I put a 2Kw fan heater on the Inverter output, the input the voltage drops to 11.5 volts and holds steady at that voltage. When I turn off the fan heater the voltage will return to over 13 volts after a very short time. I also tried it with a 3Kw kettle, the same voltage drop was seen. Batteries are getting charged up by the on-board battery charger on EHU and by 2 x 150w Solar panels.
Is it usual to see the voltage drop like this from the batteries when under a heavy load???
Liked by: Ally
Bigrigs97
Newbie
Avatar
Gender: n/a
Age: 69
Posts: 7
Registered: 04 / 2022
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 30.04.2022  ·  #2
No That's about average.
Liked by: mvnube
baguette
Eat's Sleep's craic
Avatar
Gender:
Location: Cork
Age: 74
Posts: 2939
Registered: 11 / 2011
My Motorhome: Rapido 963F
Base Vehicle: Ducato 2.8 JTD Power
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 30.04.2022  ·  #3
Normal, I've 2 X 110 ah deep cycle batteries and the same happens when I run the microwave off the 1500w inverter.
It's a lead acid thing, it doesn't happen with LiFePO4 batteries.
Liked by: Ally, mvnube, sprinter
mtravel
Love's the Craic
Avatar
Gender:
Location: Legnano, Italy
Age: 72
Posts: 219
Registered: 02 / 2020
My Motorhome: Carthago Malibu 600DB
Base Vehicle: FIat Ducato 2.3 140CV
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 01.05.2022  ·  #4
Don't come near my pitch when camping !!!

Sorry but maybe you don't realize you are seriously at risk of fire.
Not to mention the inverter efficiency (always less than one) 2KW compared to 12V are almost 170A.
Cables of only 25mm2 are madness. And the length of two meters only makes things worse.
The inverters should be placed as close as possible to the battery, connected with suitable cables (in your case you should at least double the section) and equipped with properly calculated fuses.

I conclude with a note on the battery, to give it a reasonable life expectancy it should be discharged to a maximum of 20% of its nominal capacity.
You're doing it at more than 50% and seeing as it's a heater, I guess for a long time.
JJF
Eat's Sleep's craic
Avatar
Gender: n/a
Location: Donegal
Age: 58
Homepage: MotorhomeCraic.com
Posts: 5351
Registered: 10 / 2014
My Motorhome:
Base Vehicle:
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 01.05.2022  ·  #5
Quote by mvnube

I have just bought and test rigged up a new 3000Kw pure sine wave inverter in my MoHo. I connected it up to my 3 x 115AH leasure bateries, battery age unknown. Using 25mm2 x 2m cables to the inverter.
Voltage without any load shows 13.5 volts.
When I put a 2Kw fan heater on the Inverter output, the input the voltage drops to 11.5 volts and holds steady at that voltage. When I turn off the fan heater the voltage will return to over 13 volts after a very short time. I also tried it with a 3Kw kettle, the same voltage drop was seen. Batteries are getting charged up by the on-board battery charger on EHU and by 2 x 150w Solar panels.
Is it usual to see the voltage drop like this from the batteries when under a heavy load???


Are you doing a test with the 2KW heater to test the inverter & batteries?
You don’t intend to attempt to heat the van using this method presumably?

Yes, the voltage drop you observe is correct, you are drawing MASSIVE current from the batteries under such loads.

Our advice to clients when fitting such high wattage inverters is only to use them with engine running and for the minimal amount of time possible (mostly fitted to use hairdryers).
As @mtravel states, cable runs, breakers, battery draw are all areas of concern with this installation and the use of them under heavy loads are to be avoided as much as possible or not at all if it can be avoided.
panda
Eat's Sleep's craic
Avatar
Gender:
Location: Wicklow Town
Age: 59
Posts: 3057
Registered: 08 / 2014
My Motorhome: Concerto 255
Base Vehicle: Fiat Ducato 9 spd Auto
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 01.05.2022  ·  #6
Gotta say...I was a bit surprised how anemic the factory fitted cables are going to my leisure batteries 🤔

Fair enough...I know everything on the 12V line is all LED and current draw is minimal so wires are quite adequate but if was running a 2 or 3 kilowatt inverter I'd be running 70mm2 direct to inverter from batteries...to be sure to be sure..

 
Liked by: JJF, mvnube
baguette
Eat's Sleep's craic
Avatar
Gender:
Location: Cork
Age: 74
Posts: 2939
Registered: 11 / 2011
My Motorhome: Rapido 963F
Base Vehicle: Ducato 2.8 JTD Power
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 01.05.2022  ·  #7
mvnube
Craic'er
Avatar
Gender:
Location: Kilkenny City, RoI
Age: 74
Posts: 24
Registered: 07 / 2018
My Motorhome: Rapido 990M called "Rose"
Base Vehicle: Sprinter 7.4m
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 02.05.2022  ·  #8
Thanks for all your informative answers.
As i said this was only a test setup to make sure the new inverter was working OK, as it was.The test cable run was 2m each way so a 4 m total run.
The inverter will be mounted above the 3 batteries with 2 x 35mm cables and a run of .5m each way for 1m total length.
I'm going to use a 200 amp circuit breaker in the live cable run and I'll use 35mm sq size cables. The max 240v usage will be a low wattage kettle max 1500w, 700w microwave (1100w current draw), and an 1000w induction hob. I will ONLY ever have 1 item on at any one time.
Liked by: Ally, baguette, JJF
mvnube
Craic'er
Avatar
Gender:
Location: Kilkenny City, RoI
Age: 74
Posts: 24
Registered: 07 / 2018
My Motorhome: Rapido 990M called "Rose"
Base Vehicle: Sprinter 7.4m
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 05.05.2022  ·  #9
Hymer544
Eat's Sleep's craic
Avatar
Gender:
Location: Derry/Donegal
Age: 54
Posts: 573
Registered: 08 / 2013
My Motorhome: VW Crafter
Base Vehicle: VW Crafter 2.5tdi
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 05.05.2022  ·  #10
I could well be proved wrong, but doubt very much that your battery capacity will run an induction hob for much time. Unless LifeO4 batteries are used, induction hobs will struggle. Unless you have massive charging capacity (over 50A and a very big solar array)?
Liked by: mvnube
mvnube
Craic'er
Avatar
Gender:
Location: Kilkenny City, RoI
Age: 74
Posts: 24
Registered: 07 / 2018
My Motorhome: Rapido 990M called "Rose"
Base Vehicle: Sprinter 7.4m
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 06.05.2022  ·  #11
Quote by Hymer544

I could well be proved wrong, but doubt very much that your battery capacity will run an induction hob for much time. Unless LifeO4 batteries are used, induction hobs will struggle. Unless you have massive charging capacity (over 50A and a very big solar array)?


I've yet to get or try a single portable induction hob. I wasn't expecting to cook a full lunch with one. I was hoping my 3 x 115Ah flooded batteries would have enough poke to run a one. :o
StrandCampingDoonbeg
Eat's Sleep's craic
Avatar
Gender: n/a
Location: Kilrush Co Clare
Age: 59
Posts: 2024
Registered: 05 / 2014
My Motorhome: mobilvetta mh 85
Base Vehicle: Fiat
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 06.05.2022  ·  #12
mvnube
Craic'er
Avatar
Gender:
Location: Kilkenny City, RoI
Age: 74
Posts: 24
Registered: 07 / 2018
My Motorhome: Rapido 990M called "Rose"
Base Vehicle: Sprinter 7.4m
Subject:

Re: Inverter voltage drop when using.

 ·  Posted: 06.05.2022  ·  #13
Selected quotes for multi-quoting:   0

Registered users in this topic

Currently no registered users in this section

The statistic shows who was online during the last 5 minutes. Updated every 90 seconds.