What Size Jump Starter Do I Need?

How we research

Match the pack to your engine, not to the biggest number on the box. Makers rate jump starters for a maximum engine size, and sometimes separately for petrol and diesel. Find your own engine size and fuel, then check that the pack’s rating covers both. This guide shows how, with the sources.

Last updated: 19 October 2026

Step 1: find your engine size and fuel

GOV.UK’s vehicle information service shows a vehicle’s engine size and fuel type from its registration number [1]. The page gives no unit for engine size, so check it against your handbook. If it is in cubic centimetres, divide by 1,000 to get litres, so 1,600 cc is 1.6 litres.

Step 2: check the pack’s rating

Look for the engine size limit on the maker’s or seller’s page, for your fuel. Two examples from a UK seller’s listings [2][3]:

  • NOCO GB20: petrol up to 4.0 litres, no diesel limit listed [2].
  • NOCO GB50: petrol up to 7.0 litres, diesel up to 4.5 litres [3].

If a pack lists no limit for your fuel, as the GB20 listing does for diesel, the listing does not show that it suits your engine [2]. Ask the seller or the maker before you buy.

A worked example

A driver has a 1.6 litre petrol car and a friend has a 2.0 litre diesel. A pack rated for petrol up to 4.0 litres covers the first car, since 1.6 is under 4.0. The same pack lists no diesel rating, so it does not cover the second car. A pack rated for diesel up to 4.5 litres covers the 2.0 litre diesel with 2.5 litres to spare.

Illustrative scenario: figures are examples, not quotes, valuations or market prices.

Why peak amps mislead

Packs often advertise “peak amps”. A seller’s own blog says this is a very brief burst, not the sustained current an engine needs to turn over, and that there is no industry-wide test standard, so two packs with very different peak figures can perform similarly [4]. The same blog advises choosing a pack that lists diesel compatibility if you drive a diesel, and one with a published cranking-amp rating rather than peak amps alone [4]. It is a seller’s blog, so treat it as one view. We do not give a table of amps by engine size, because we found no neutral source for one.

Hybrids and electric cars

The RAC says that on a hybrid you can jump start the 12V battery only, and to check the owner’s manual [5]. Both the RAC and the AA say not to use a hybrid or electric car as the donor vehicle [5][6]. A jump starter pack does not need a donor car, but the rating on the box is for the engine, so check your manual for what the car allows.

Using it

  • Check the pack is fully charged first [5][6].
  • Check for obvious damage to the batteries or leads. Do not jump start if there is any [5].
  • Put the pack on the ground or somewhere stable, not on the engine, because it could fall off when the engine starts [5][6].
  • The AA says to switch off the pack after 5 minutes, let the engine run another 5 to 10 minutes, then drive normally, not in stop-start traffic, for at least 30 minutes to recharge the battery [6].

Recalls and safety

We searched the official recalls list for “jump starter” on 19 October 2026. It returned 19 reports, six of the first eight being jump starters. They include recalls of the Ring RPPL360 Fast Charge Lithium Jump Starter on 27 March 2023, a multi-function jump starter on 18 April 2023 and a Fast Charge Jump Starter 260 and power bank on 1 March 2024 [7]. Search the official recalls list for your brand and model. Our product safety and recalls page explains how we check. Recalls checked 19 October 2026.

Questions people ask

Can I use a bigger jump starter than my engine needs?

Our sources do not say whether this causes problems. The ratings are given as maximum engine sizes, so a pack rated for a larger engine than yours is within its stated limit [2][3]. Check the maker’s instructions.

Does a diesel need a bigger pack than a petrol?

Makers often rate diesel lower, as the GB50 listing does at 4.5 litres against 7.0 litres for petrol [3]. One seller’s blog says diesels need more sustained cranking power because of higher compression [4]. Always check the diesel rating, not the petrol one.

Are peak amps the number to compare?

Not on their own. A seller’s blog says there is no standard test for peak amps and that two packs with very different figures can perform similarly [4].

Should I use leads or a pack?

The RAC says a pack lets you start the car without another vehicle, which helps if you cannot get help from another driver [5].

Sources

  1. Get vehicle information from DVLA, GOV.UK, gov.uk. The page shows no date. Checked 19 October 2026.
  2. NOCO GB20 Boost Sport 500A jump starter, Tayna (UK seller listing), tayna.co.uk. Checked 19 October 2026.
  3. NOCO GB50 Boost XL 1500A jump starter, Tayna (UK seller listing), tayna.co.uk. Checked 19 October 2026.
  4. Sizing a jump starter correctly: peak amps, CCA and the numbers sellers don’t explain, WOLFBOX (seller’s own blog). Dated 7 August 2026, wolfbox.com. Checked 19 October 2026.
  5. How to jump start a car in 10 steps, RAC Drive. Dated 10 September 2026, rac.co.uk. Checked 19 October 2026.
  6. How to jump start a car, The AA. Last updated 26 June 2024, theaa.com. Checked 19 October 2026.
  7. Product safety alerts, reports and recalls, Office for Product Safety and Standards, GOV.UK. Searched 19 October 2026.