Choosing a reliable inverter for your Motorhome (1 Viewer)

Markpd

Free Member
Oct 15, 2022
4
1
Surrey, UK
Funster No
91,910
MH
Don't own one
Hi
Hopefully I won't get auto-banned this time! lol
Bit of a random post this as I don't even own a MH :oops: , but I'm hoping there's plenty of folk here with experience with inverters who can help, as their seems to be a near total absence of any websites actually testing them! (not just reviewing their features and price, and then proclaiming them great!).
Normally when I buy, e.g computer hardware, like power supplies, I can find at least several websites that do actual load testing, oscilloscope and temperature testing etc. For inverters I found practically nothing! Wth?? (other than the odd random youtuber, 1 of whom showed just how rubbish a Bestec 500w 'pure' sinewave inverter was on his scope! Although 1 other test showed the Bestec 300w seemed to be ok).

Anyway, I've read through dozens of threads here and haven't found a definitive list of what's considered good quality inverters, people did ask, but I only saw 3 manufactures suggested. Victron, Sterling and Merlin. Are their no other decent brands I could consider?
I have an old Waeco battery charger btw, and that's served me well. I believe that they (who are now Dometic) build decent quality kit, how about their inverters?

My usage of an inverter will be somewhat random and infrequent, but with that said I want clean pure sine wave AC power (not the noisy rubbish Bestec apparently do). Hence looking at better brands, I'm willing to pay a little more upfront for it, that said, I don't think I need a 'Rolls-Royce' inverter ;).

My main* intended use is to provide backup power (for upto a few hours should we get power cuts this or future winters, plus we get occasional short power cuts here anyway) to my small fridge/freezer (rated at 0.6A, so for 230v that's 138w right?) and my small freezer rated at 85w for a total continuos running power of ~223w. I understand that startup power can be upto 'several' times more (can anyone be more specific?).
(Oh and I have two 70 Ah batteries I can use for this, their not new, but my battery tester shows them both with about 82% capacity, so will hopefully suffice. And I don't mind taking them below 50% capacity for the rare times that I'll be using them as backup power).
*I will likely use it for the other random things too.

Would a 300w cont, 600w peak inverter be sufficient for that? Or do I need to step up to a 600w cont to 1200w peak inverter?

Some prices,
Victron 12v 375VA (300w-700w pk, zero load 5.6w) £118, 12v500VA (400w-900w pk, zero load 6w) £137 (5yr warrantee!)
Sterling 12v 300w (600w pk, no load 0.95A) £150!, 600w (1200w pk, no load 0.95A) £224!! (not getting that one!)
Merlin (now Kisae, is that right?) 12v 400w (800w pk, zero load <0.8A) £215!!, 600w (1200w pk, zero load <0.8A) £283!!! (nor getting these!)
Dometic 12v 350w (700w pk, zero load 0.6A) £134, 12v 600w (1200w, zero load 0.8A) £301!!!

Actually, it would seem if I need a 600/1200w inverter, the only real choice is the Victron (seeing as I've been quoted a good price for a new one, as above, ebay offer). Unless I'm missing out on any other decent makes?

Btw, a friend of mine (whose converting a DD bus to a MH) recommends <Broken link removed>, but theirs no clue as to who makes their inverters (I've since emailed them and they won't disclose who makes them, other than a reputable "reputable factory in China"), any thoughts?
And are Ring inverters any good?

Sorry for the massive post!
TIA, Mark
 
Apr 27, 2016
6,939
8,103
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
My main* intended use is to provide backup power (for upto a few hours should we get power cuts this or future winters, plus we get occasional short power cuts here anyway) to my small fridge/freezer (rated at 0.6A, so for 230v that's 138w right?) and my small freezer rated at 85w for a total continuos running power of ~223w.
The inverter needs to be able to supply both appliances at the same time, so that's say 240W, which is 240 / 12 = 20A at 12V. With two 70A batteries (let's say 60Ah capacity) it would take 60 / 20 = 3 hours to discharge down to the 50% level.

The maximum recommended amps from the batteries is about C/5, where C is the Ah capacity. So for 120Ah the max amps would be 120/5 = 24A, which means the 20A demand would be within the recommended limits.

In reality the thermostats would cut in and would probably only be demanding power for half or even a third of the time, especially if they were already cooled to a steady state and the doors were not opened too often.

Victron inverters have a big transformer inside, which increases the weight and cost, but is much better at coping with switch-on surges. They are very good quality, and it's what I would choose. The 300W version would cope with the two fridge/freezers you mentioned.

You could also consider a Multiplus combined inverter/charger, especially if you intend to grow your system in the future. You could run the appliances permanently from the output, and it would automatically switch over to inverter if the power failed. When the power comes back on, it would automatically switch back to mains, and recharge the batteries ready for the next power cut.
 
Last edited:
May 7, 2016
7,369
11,949
West Sussex
Funster No
42,951
MH
Malibu Van 640 LE K
Exp
Since 2003
Very happy with my Victron inverter. My Sterling one went up in a puff of smoke, might have been user error but it didn’t seem to have any self protection.
 

Stealaway

Free Member
Jan 8, 2013
8,496
11,538
Dronfield - Derbyshire
Funster No
24,202
MH
Burstner Lyseo 690G
Exp
Happy FLT since 2011
I would be investing in a bigger battery bank first, yours are not nearly big enough.
There are many 1000 watt model and being an optimum size buy the biggest physical sized one for less than £100.
I've had a cheap Chinese one for 10 years, for more than 3000 hours and the cooling fan is just starting to get noisy .

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Hoovie

Free Member
May 16, 2021
1,249
1,689
Funster No
81,251
MH
Autotrail
Hi
Hopefully I won't get auto-banned this time! lol
Bit of a random post this as I don't even own a MH :oops: , but I'm hoping there's plenty of folk here with experience with inverters who can help, as their seems to be a near total absence of any websites actually testing them! (not just reviewing their features and price, and then proclaiming them great!).
Normally when I buy, e.g computer hardware, like power supplies, I can find at least several websites that do actual load testing, oscilloscope and temperature testing etc. For inverters I found practically nothing! Wth?? (other than the odd random youtuber, 1 of whom showed just how rubbish a Bestec 500w 'pure' sinewave inverter was on his scope! Although 1 other test showed the Bestec 300w seemed to be ok).

Anyway, I've read through dozens of threads here and haven't found a definitive list of what's considered good quality inverters, people did ask, but I only saw 3 manufactures suggested. Victron, Sterling and Merlin. Are their no other decent brands I could consider?
I have an old Waeco battery charger btw, and that's served me well. I believe that they (who are now Dometic) build decent quality kit, how about their inverters?

My usage of an inverter will be somewhat random and infrequent, but with that said I want clean pure sine wave AC power (not the noisy rubbish Bestec apparently do). Hence looking at better brands, I'm willing to pay a little more upfront for it, that said, I don't think I need a 'Rolls-Royce' inverter ;).

My main* intended use is to provide backup power (for upto a few hours should we get power cuts this or future winters, plus we get occasional short power cuts here anyway) to my small fridge/freezer (rated at 0.6A, so for 230v that's 138w right?) and my small freezer rated at 85w for a total continuos running power of ~223w. I understand that startup power can be upto 'several' times more (can anyone be more specific?).
(Oh and I have two 70 Ah batteries I can use for this, their not new, but my battery tester shows them both with about 82% capacity, so will hopefully suffice. And I don't mind taking them below 50% capacity for the rare times that I'll be using them as backup power).
*I will likely use it for the other random things too.
OK, A key purpose of the Inverter will be to support an AC Compressor Fridge? You are already aware that there is a startup power "several" times more than the usual running power. This is a important thing to be aware of, so that is great, but you don't know how much "several" is....
It can vary between models depending on the Compressor, but it is a BIG difference of up to and possibly greater than 20x the running power!
Here is a bit of video I did showing the draw on an inverter when running an AC Fridge. There is no commentary, but keep an eye on the time and refer to the notes in the video - copied below also

Times:
0:05 - Inverter Switched On
0:20 - Fridge Plugged in
0:30 - Fridge Door Opened (so Light comes on)
0:41 - Fridge Temp Dial turned to Max - Compressor In-rush Current comes on
0:45 - In-Rush Current ends

Note that the power use you are seeing from 0:45 is the maximum power draw all the time the fridge is actively cooling, which is a small percentage of the time on a Compressor Fridge (this is what makes them so efficient in use).


I'll comment on the inverter requirements next
Would a 300w cont, 600w peak inverter be sufficient for that? Or do I need to step up to a 600w cont to 1200w peak inverter?

Some prices,
Victron 12v 375VA (300w-700w pk, zero load 5.6w) £118, 12v500VA (400w-900w pk, zero load 6w) £137 (5yr warrantee!)
Sterling 12v 300w (600w pk, no load 0.95A) £150!, 600w (1200w pk, no load 0.95A) £224!! (not getting that one!)
Merlin (now Kisae, is that right?) 12v 400w (800w pk, zero load <0.8A) £215!!, 600w (1200w pk, zero load <0.8A) £283!!! (nor getting these!)
Dometic 12v 350w (700w pk, zero load 0.6A) £134, 12v 600w (1200w, zero load 0.8A) £301!!!

Actually, it would seem if I need a 600/1200w inverter, the only real choice is the Victron (seeing as I've been quoted a good price for a new one, as above, ebay offer). Unless I'm missing out on any other decent makes?
I looked at various inverters and in the end I settled on Victron. Did this for a number of reasons - Brand Quality; 5 Year Warranty; Very high peak power capability (most inverters quote a peak of twice the power and that peak is either not achievable or is only for milliseconds. The Victron Peak is >2x the power and can last upto 30 seconds); Designed to run 24/7 non-stop.
I went through the various sizes of Victron Phoenix inverters to see the lowest I could get away with to support the fridge....
12/250VA - Non-Starter
12/375VA - Non-Starter. The Peak Power of 700W was not enough to start the compressor
12/500VA - This is a 400W Inverter with a peak of 900W. Now this did the job generally. The Fridge always started without a problem. However ... Each time the fridge started, the Inverter would report 'Overload' and would give a shudder. I went with the 12/500 as the next step up to 12/800 was significantly more expensive and the 12/500 DID work.
I do know of someone who bought the same Fridge as mine and he found the 12/500 and his fridge was not such a great match, so it could be borderline? The fridge I had was significantly more efficient than the one have going by the figures, so YOUR fridge could have a higher in-rush current and the 12/500 would not do the job.
12/800VA - No problems, generally no overload reported. I had a 12/800 (actually a Multiplus 12/800/35) for a short time and it was good, but I actually decided to get a 12/3000/120 to consolidate the Fridge Inverter and High Power Inverter, so only used the 12/800 for a brief period.
Of the Victron range, for your purpose, I would recommend the 12/800 or maybe in fact the 12/1200 as the price of the two are usually quite close and the extra power of the 12/1200 can be handy (it is a big old boy though, but guess not a problem if fitting in a house room?)

I posted a little article on my website back in 2018 about AC Fridges in campers if you are bored and want something to read sometime :) - see https://www.wildebus.com/a-home-fridge-in-a-campervan/

Btw, a friend of mine (whose converting a DD bus to a MH) recommends <Broken link removed>, but theirs no clue as to who makes their inverters (I've since emailed them and they won't disclose who makes them, other than a reputable "reputable factory in China"), any thoughts?
And are Ring inverters any good?

Sorry for the massive post!
TIA, Mark
Photonic Universe are a reliable company and they will have checked the products they are buying in to resell to a decent degree, as opposed to your typical eBay seller who would be just a importer/reseller and has no control or real knowledge of the specific item.
Another good reliable company is Alpha Batteries, and they have their own brand of Inverters, which look remarkably similar to the ones from Photonic, but better priced - https://www.alpha-batteries.co.uk/shop/?s=xplorer+inverter&post_type=product . I recommended one of these to someone (who is a member here as well actually) when he didn't want to pay the premium for a Victron.

I have looked at various inverters and the only ones I would sell are the Victron ones and the ones that Photonic and Alpha sell (and only then if the customer insists on not stumping up for Victron). Inverters are possibly the most variable product of all in the Motorhome/Camping/Boating/RV world and is a complete lottery. It is very very easy to spend and waste a load of money on total rubbish.
Just spend it on something known to be good to start with!
 

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